There are about thirty species in the genus Dahlia, and over 20,000 cultivars are grown today. These tuberous plants are popular for their amazing range of colors and flower shapes.
Dahlias are native to the subtropical regions of Central and South America. They were important as a root crop and as a medicinal plant among the pre-Columbian Indians. Dahlia imperialis, the "tree dahlia", had hollow stems up to twenty feet long which were used for hauling water; the Aztec name was acocotli, or "water-cane".
Spanish invaders catalogued several kinds of dahlias and sent plants back to the Royal Botanical Gardens in Madrid. The species was named after Swedish botanist Anders Dahl. European breeders produced double flowered dahlias by the early 18th century, and the plant was very popular between 1810 and 1840. In 1872, a Dahlia juarezii tuber survived shipment from Mexico to Holland, and its brilliant red flower with pointed petals captivated breeders. Soon this new species was crossbred with cultivated varieties, leading to the thousands of cultivars being grown today